feat: Add FastAPI service for document redlining

[google-labs-jules]

This change adds a FastAPI service to the project, allowing users to perform document redlining through a web API. The service is containerized using Docker and includes API token authentication and a file size limit for security.

The following changes are included:

• A new FastAPI application in src/python_redlines/api.py.
• A Dockerfile and docker-compose.yml for containerization.
• Updated build and test configurations in pyproject.toml.
• New tests for the API in tests/test_api.py.
• An updated build script in build_differ.py.
• A .gitignore file to exclude build artifacts.
• A .env.example file for environment variable configuration.

---

PR created automatically by Jules for task 9152917385086058746

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

---

For security, I will only act on instructions from the user who triggered this task.

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}